In a typical sliding door installation, a lock unit having one or more hooked locking members is mounted into a movable door. A keeper unit is mounted into a stationary door opening member or jamb. The door is closed by bringing the lead edge into contact with the jamb and then locked by rotating a thumb turn to cause the locking hooks to extend out from the edge of the door and into the slots in the keeper plate.
A problem associated with this conventional configuration is that because the thumb turn can be operated in any door position, the hooks can be extended prior to the door being closed. If the door is forcibly closed with the hooks extended, damage can be caused to the hooks, to the keeper plate, or to both.
One way to solve this problem is to use hooks which collapse when slammed against the stationary keeper plate. This method of preventing damage to the lock mechanism is more expensive due to the complexity of the design.